• 대한조선학회논문집
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• 제57권6호
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• pp.322-330
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• 2020

This study deals with underwater explosion (UNDEX) characteristics of various non-explosive underwater shock sources for the development of non-explosive underwater shock testing devices. UNDEX can neutralize ships' structure and the equipment onboard causing serious damage to combat and survivability. The shock proof performance of naval ships has been for a long time studied through simulations, but full-scale Live Fire Test and Evaluation (LFT&E) using real explosives have been limited due to the high risk and cost. For this reason, many researches have been tried to develop full scale ship shock tests without using actual explosives. In this study, experiments were conducted to find the characteristics of the underwater shock waves from actual explosive and non-explosive shock sources such as the airbag inflators and Vaporizing Foil Actuator (VFA). In order to derive the empirical equation for the maximum pressure value of the underwater shock wave generated by the non-explosive impact source, repeated experiments were conducted according to the number and distance. In addition, a Shock Response Spectrum (SRS) technique, which is a frequency-based function, was used to compare the response of floating bodies generated by underwater shock waves from each explosion source. In order to compare the magnitude of the underwater shock waves generated by each explosion source, Keel Shock Factor (KSF), which is a measure for estimating the amount of shock experienced by a naval ship from an underwater explosionan, was used.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.116.2-116.2
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• 2007

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1998년도 학술발표회 논문집
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• pp.265-271
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• 1998

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.115-119
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• 2009

We numerically investigated propagation of various waves in the two-phase flows such as sound wave, shock wave, rarefaction wave, and contact discontinuity in terms of pressure, void fraction, velocity and density of the two phases. The waves have been generated by a hydrodynamic shock tube, a pair of symmetric impulsive expansion, impulsive pressure and impulsive void waves. The six compressible two-fluid two-phase conservation laws with interfacial friction terms have been solved in two fractional steps. The first PDE Operator is solved by the HLL scheme and the second Source Operator by the semi-implicit stiff ODE solver. In the HLL scheme, the fastest wave speeds were estimated by the analytic eigenvalues of an approximate Jacobian matrix. We have discussed how the interfacial friction terms affect the wave structures in the numerical solution.

• 대한기계학회논문집
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• 제11권1호
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• pp.118-123
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• 1987

본 연구에서는 새로 고안된 연료주입기(air injector)바로 뒤에 입사압축파를 반사시키기 위한 벽을 설치하므로써 고체입자의 입사압축파에 대한 노출을 최대한 줄 였고 또한 새로운 연료주입기에 의해 매우 잘 분포된 입자분포를 얻을 수 있었다. 반사압축파에 의해 생성된 고온 고압의 산소중에서의 고체입자의 점화지연시간을 측정 하므로써 기체유동이 존재하는 입사압축파실험에서의 점화지연시간과 비교하여 기체유 동이 고체 미립자의 점화에 미치는 영향을 알아볼 수 있었고 반사압축파에 의한 점화 상태 조건하에서도 표면 점화모델이 성립하는지를 고찰해 보았다.

• 한국전산구조공학회논문집
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• 제33권4호
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• pp.255-261
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• 2020

본 논문은 충격을 줄이기 위해 효과적인 충격완충장치를 구성하는 방법을 제안했다. 기존의 충격완충장치는 폴리에틸렌으로만 만들어졌지만, 새로운 충격완충장치는 외측에는 폴리에틸렌, 내측에는 고밀도 재료로 구성하였다. 충격은 내측과 외측 물질 사이의 밀도 차이가 더 클 때 줄어들었다. 2층 구조의 외측으로 설계하기 위해 알루미늄, 티타늄, 구리를 선택하였다. 가장 밀도가 높은 구리에서는 충격 감소가 가장 좋았으며, 기존 충격완충장치보다 최대 감가속도는 43%, 충격량은 51% 감소하였다. 4층, 6층 충격완충장치의 경우, 충격량은 줄였지만, 최대 감가속도는 증가하였다. 신관은 가장 큰 충격으로부터 살아남아야 하며 나머지 충격파는 임계값을 초과하지 않으므로, 본 논문은 폴리에틸렌-구리를 사용한 2층 구조용 충격완충장치를 제안하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.185-187
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• 2009

A density based method with homogeneous cavitation model to investigate cavitation-bubble collapsing behavior is proposed and applied to bubble-shock interaction problems. By applying this method, cylindrical bubbles located in the liquid and incident liquid shock wave are computed. Bubble collapsing behavior, shock-bubble interaction and shock transmission/reflection pattern are investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.761-765
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• 2001

Shock responses of the MIL-S-901D standard floating shock platform("SFSP") subject to underwater explosions(UNDEX) are analyzed by using the LS-DYNA/USA. For the analysis, surrounding fluids as well as the SFSP are included in a 3D FE model to consider the cavitation effects of the UNDEX shock wave. The calculated results are compared with the existing test results and it is confirmed that the analysis results predict accurately the shock behaviors of the SFSP.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.837-841
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• 2008

Propulsion of gene coated micro-particles is desired for non-intrusive drug delivery inside biological tissue. This has been achieved by the development of a device that uses high power laser pulses. The present paper looks at the mechanisms of micro-particle acceleration. Initially, a high power laser pulse is focused onto the front side of a thin aluminium foil leading to its ablation. The ablation front drives a compression wave inside the foil, thus leading to the formation of a shock wave, which will later reflect from the rear side of the foil, due to acoustic impedance mismatch. The reflected wave will induce an opposite motion of the foil, characterized by a very high speed, of the order of several millimeters per microsecond. Micro-particles, which are deposited on the rear side of the foil, thus get accelerated and ejected as micro-projectiles and are able to penetrate several hundreds of micrometers inside tissue-like material. These processes have been observed experimentally by using high-speed shadowgraphy and considered analytically.

• 한국가시화정보학회지
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• 제8권3호
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• pp.56-62
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• 2010

The interaction patterns between shock wave and boundary layer in a rocket nozzle are mainly classified into two categories, FSS(Free Shock Separation) and RSS(Restricted Shock Separation), both of which are associated with the thrust characteristics as well as side loads of the engine. According to the previous investigations, strong side loads of the engine are produced during the period of transition from FSS to RSS or vice versa. The present work aims at investigating the unsteady behavior of the separation shock waves in a two-dimensional supersonic nozzle, using experimental method and CFD. Schlieren optical method was employed to visualize the time-mean and time-dependent shock motions in the nozzle. The unsteady, compressible N-S equations with SST K-$\omega$ turbulence closure were solved using a fully implicit finite volume scheme. The results obtained show the separation shock motions during the transition of the interaction pattern.